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SubjectRe: [Update] Re: [PATCH v3]PM/Sleep: Timer quiesce in freeze state
On Fri, Feb 06, 2015 at 05:14:54PM +0100, Peter Zijlstra wrote:
> On Fri, Feb 06, 2015 at 02:20:13AM +0100, Rafael J. Wysocki wrote:
> > void freeze_wake(void)
> > {
> > + unsigned long flags;
> > +
> > + spin_lock_irqsave(&suspend_freeze_lock, flags);
> > + if (suspend_freeze_state > FREEZE_STATE_NONE) {
> > + suspend_freeze_state = FREEZE_STATE_WAKE;
> > + wake_up(&suspend_freeze_wait_head);
> > + }
> > + spin_unlock_irqrestore(&suspend_freeze_lock, flags);
> > }
>
>
> > +static void enter_freeze_proper(struct cpuidle_driver *drv,
> > + struct cpuidle_device *dev, int index)
> > +{
> > + tick_freeze();
> > + drv->states[index].enter_freeze(dev, drv, index);
> > + /*
> > + * timekeeping_resume() that will be called by tick_unfreeze() for the
> > + * last CPU executing it calls functions containing RCU read-side
> > + * critical sections, so tell RCU about that.
> > + */
> > + RCU_NONIDLE(tick_unfreeze());
> > +}
>
> So I'm a wee bit confused; if we use an enter_freeze() state that keeps
> interrupts disabled; who is going to call the freeze_wake() thing?

Ah, I think I see, so we wake up, keep the interrupt pending, re-enable
the tick and time and everybody, then re-enable interrupts, take the
interrupt and go around the idle loop to find we need a reschedule etc..


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